This invention relates generally to a radio frequency spectrum manager and spectrum management method for a communication network. In particular, the invention relates to a radio frequency spectrum manager and spectrum management method for a hybrid optical fiber/coaxial cable communication network delivering two-way digital and/or analog information streams.
Existing cable networks provide analog cable television programming from a central source location (known as the "head end") to multiple users in receiver locations such as homes, business, etc., for display on television sets. Some receiver locations are able to send information back to the head end, usually through use of a set-top converter box. This return information can be in the nature of a request for certain programming from the head end, e.g., a pay-per-view program.
The forward and reverse information streams are typically transmitted between the head end and the receiver locations over a network of coaxial cable and/or optical fibers. The information streams are formed into radio frequency bands, such as by the use of Quadrature Amplitude Modulation (QAM), before transmission. The signals are demodulated into a usable form at the receiving end.
Most prior art cable networks provide their analog video programming to users within a first dedicated spectrum band and receive return information from users within a second dedicated spectrum band. The video programming is arranged in preset channels (e.g., 6 MHz channels) within the forward spectrum band so that the receiving television set can be tuned to display the desired program.
New cable networks have been proposed to deliver a combination of analog and digital information to a user in a home or other location and to receive analog and/or digital information from the user. These cable networks may provide a combination of digital and analog television programming, video-on demand, home shopping services, interactive video games, telephone service, etc. While most of this information will be transmitted from a distribution hub or head end to multiple users, a significant stream of information will be transmitted in the reverse direction from the users to the distribution hub. Similar concepts have been proposed for transmission of these services and information over telephone lines.
Baji et al. U.S. Pat. No. 5,027,400 describes a cable communication system that permits the insertion of commercial advertisements into video programming at a subscriber's request. In one embodiment (shown in FIGS. 2--2 and 26 and described at col. 17, line 49), the system uses a traffic monitor/channel exchange control unit to dynamically change allocated channels. The control unit monitors requests from subscribers, the amount of video data to be transferred, etc., to issue an exchange control signal for establishing an optimal channel share condition.
Pocock et al. U.S. Pat. No. 5,014,125 describes an interactive television system in which a subscriber can request a particular program or application from sources at a head end. Once a logging and initiation procedure has been completed, a navigation session task selects and opens a viewing session with a video display task which communicates with a control unit. The video display task is supplied with the user terminal address and the transmission path ID for the session. If the channel specified by the transmission path ID is operating at full capacity, and if transmission capacity is available on an alternate channel, the video display task can send a control message to the user terminal to instruct it to tune to an alternate channel.